Switching device



y 1949. L. E. 01.5%: ETAL 2,471,281

SWITCHING DEVICE Filed Aug. 27, 1947 INVENTORS RICHARD WERTZLER LEONARDE, OLSON ATTORNEYS Patented May 24, 1949 SWITCHING DEVICE Leonard EugeneOlson and Richard Wertzler, Chicago, Ill., assignors to SinclairRefining Company, New York, N. Y., a corporation of Maine ApplicationAugust 27, 1947, Serial No. 770,932

(Cl. ZOO-81.6)

2 Claims. 1

This invention relates to switches and like devices actuated by movementof a liquid in a U- tube and has for its object the provision of animproved device of this character. The invention is particularlyconcerned with devices having switch means including a conducting liquidsuch as mercury in the U-tube and an electrical circuit which is openedand closed by movement of the mercury, and provides means in combinationwith such devices for operating the switch means on failure of the flowof liquid which actuates the device.

Our invention provides a very simple and positive switch means forprotecting apparatus and operations dependent upon a continuous flow ofliquid, such as cooling water. In an advantageous embodiment, our deviceis in the form of a cut-off switch comprising a U-tube in which themercury is held in one operating position by the pressure of the flowingliquid but is moved to another operating position by failure of the flowof liquid. The U-tube is so constructed that it is continuously suppliedwith the liquid which holds the mercury in operating position while theliquid is flowing, but is emptied of liquid by drainage when the liquidceases to flow. We provide a low level outlet or bleeder for the tubewhich is always open and a high level outlet as an overflow forcontrolling the pressure imposed on the mercury and a vent to ensurepositive drainage through the low outlet.

The accompanying drawings illustrate in side elevation a switch deviceof our invention in the form of a cut-ofi switch. It will be apparentthat the electrical terminals and mercury can be arranged to switch onor ofi, close or open the circuit, on failure of the flow of liquid.

The device illustrated in the drawings comprises a U-tube l of, say, 12mm. glass tubing with a short leg 2 in which is sealed the tungstencontact leads 3 and 4 of the electric circuit 5. The long leg 6 extendssome 30 cm. above the short leg and has a lower drain extension 1, anupper drain extension 8, a vent 9, and an inlet connection Hi, allpreferably an integral part of the tube. The body of mercury I2 is shownin its position of rest with only the small residue of water l3 in thebottom of the long leg 6. In this position the mercury is out of contactwith contact 3 and the circuit is broken. The low outlet hole [4- of theextension I is quite small, say, 2 mm. in diameter, and servesessentially as a bleeder for the long leg. The hole I in the drainextension 8 is larger than hole l4 and serves as an overflow to regulatethe pressure of liquid acting on the mercury. Hole 15 may be about 30cm. above hole I l. The vent 9 is about 1 to 2 mm. in diameter andserves to insure positive drainage of leg 6 through hole [4. The inletIt! may be connected by a hose or the like to the conduit through whichthe liquid is flowing. This liquid may be for cooling condensers,chemical equipment, and the like, the interruption of which may causeserious damage. By means of a valve (not shown) the flow of liquid intothe long leg is controlled so that there is a continuous overflowthrough hole 15. This insures suflicient pressure on the mercury to holdit in contact with contact 3. Drain extensions 1 and 8 may be connectedby rubber tubing to a waste line.

When the liquid ceases to flow, the liquid in the line to be protecteddrains out of the long leg 5 through hole M, the vent 9 preventingwaterlock and the retention of liquid in the leg.

If the power load is too heavy to be connected directly through themercury in the tube, a suitable relay system may be inserted in thecircuit and the leads of circuit 5 need only be connected in series withthe circuit.

We claim:

1. A liquid-flow failure switch comprising a U- tube of electricallynon-conducting material having a short leg and a long leg, a body ofmercury in the tube, electric contact means in the tube actuated by themercury, inlet means on the lon leg for receiving liquid flowing in aconduit, means for the continuous removal of liquid from the long legwhereby a constant pressure of liquid is maintained on the mercury, avent in the upper part of the long leg to insure drainage of the longleg, and a drain means which is continuously open on the long leg forremoving liquid on failure of the flow in the conduit to change theposition of the mercury.

2. A liquid-flow failure switch comprising a U- tube of electricallynon-conducting material having a short leg and a long leg, a body ofmercury in the tube, electric contact means in the tube actuated by themercury, inlet means on the long leg for receiving liquid flowing in aconduit, an extension of the long leg having an upwardly extending ventand a lower outlet for the continuous removal of liquid from the longleg whereby a constant pressure of liquid is maintained on the mercury,and a drain means having a continuously open hole near the lower part ofthe long leg for removing the liquid therefrom on failure of the flow ofliquid to decrease the pressure on the mercury.

The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Date Hickman Feb. 12, 1935 Number

